Cigarette filters

ABSTRACT

Cross-flow filter elements for cigarettes are made by forming a continuous rod of filter material including a number of substantially axial grooves separated by rib portions; closing alternate grooves at regular intervals by pinching together the ribs; and cutting the rod at regular intervals to form a succession of cross-flow filter elements. The rod is preferably formed by folding inwards circumferentially spaced regions of a continuous tube which itself is formed by bringing together the edges of a continuous web of filter material.

ited tates atet, [1 1 Molins et a1.

[ CIGARETTE FILTERS [75] Inventors: Desmond Walter Molins, London,England; Francis Auguste Maurice Labbe, Neuillysur-Seine, France; ClivePerkins, London, England [73] Assignee: Molins Limited, London, England[22] Filed: Nov. 3, 1971 [21] Appl. No.: 195,177

[30] Foreign Application Priority Data Nov. 9, 1970 Great Britain..53,274/70 [52] US. Cl. ..93/1C, 93/77 FT, 93/84 TW, 7 156/211, 156/465[51] llnt. Cl ..B31c 13/00 [58] Field of Search ..93/l C, 1 F, 19,93/20, 77 PT, 84 TW; 156/465,, 211

- [56] References Cited UNITED STATES PATENTS 3,128,680 4/1964 Schaaf,Jr. ..93 1 c 3,205,791 9/1965 Goodfellow et a1 ..93/l C 3,383,449 5/1968Muller t ..93/1 C X 3,638,661 2/1972 Pinkham ..93/l C X PrimaryExaminer-Andrew R. Juhasz Assistant Examiner-James F. Coan Attorney-NeilF. Markva et a1.

[57] ABSTRACT 7 Claims, 12 Drawing Figures PAIENIEUW 3,735,672

SHEET 1 OF 2 PAH-1mm mzslsns SHEET 2 OF 2 This invention is concernedwith filters for cigarettes and other similar articles (i.e. forsmoking), comprising a filter element formed with a number of axiallyextending peripheral grooves of which alternate grooves are closed atopposite ends, so that the smoke enters the filter through one set ofalternate grooves and leaves the filter through the other set of groovesafter passing transversely through the rib portions between the grooves.A filter in this form will be referred to as a cross-flow filter.

According to one aspect of this invention, filter elements forcross-flow filters are made by forming a continuous rod of filtermaterial including a number of substantially axial grooves separated byrib portions; closing alternate grooves at regular intervals by pinchingtogether the ribs; and cutting the rod at regular intervals to form asuccession of cross-flow filter elements.

If the filter elements are needed for filter-tipped cigarettes, the rodis preferably enclosed in a tubular wrapping before it is cut to formindividual filters; these filters can then be joined to cigarettes inthe usual way. Alternatively a filter element made in this way could,for example, be inserted into a plastic mouthpiece which a user canhimself push over the end of a cigarette before smoking it.

The continuous grooved rod is preferably formed by folding inwardscircumferentially spaced regions of a continuous tube. The tube may beformed by extruding filtermaterial (e.g. fibrous cellulose acetate withan appropriate bonding agent) into a tubular section. Preferably,however, the continuous tube is formed by bringing together the edges ofa continuous web of filter material, for example of fibrous celluloseacetate or paper; in this case the web may be shaped in cross-section ormay be scored longitudinally (especially in the case of paper) so as topromote folding along the required lines.

Filter material consisting of continuous crimped fibers of celluloseacetate may, for example, be used with a thermoplastic resinous bondingagent or with a bonding agent in the form of a volatile solvent. In theformer case heat is applied at an appropriate region to melt the bondingagent, which then sets and joins the cellulose fibers after cooling. Inthe case of a bonding agent in the form of a volatile solvent (sometimesreferred to as a plasticizer) the surfaces of the fibers are made tackyby the solvent and are then set by driving off the solvent by means ofheat.

After the ribs have been pinched together at the appropriate regularintervals, the filter element may be set by the application of heat(especially in the case of cellulose acetate provided with aplasticizer). Alternatively, they may beset by means of an adhesive(especially in the case of paper) which may be applied between thepinched-together rib portions to hold these portions together; heat maybe applied to set or activate the adhesive.

According to another aspect of this invention a crossflow filter elementcomprises a 'rod formed with substantially axial grooves separated byrib portions which contact one another at the ends of the rod so as toclose alternate grooves at opposite ends of the rod.

Examples according to the present invention will now be described withreference to the accompanying drawings. In these drawings:

FIG. 1 is a side view of a cross-flow filter element according to thisinvention;

FIGS. 2 to 4 are sections respectively on the lines II- -II, III--IIIand IV-IV in FIG. 1;

FIG. 5 shows how the filter element is initially formed by folding atube of circular cross-section;

FIG. 6 shows how alternate ribs are pinched together to close the axialgrooves at regular intervals;

FIG. 7 is a side view of one of the wheels which pinches the ribstogether;

FIG. 8 is a view in the direction of the arrow VIII in FIG. 7;

FIG. 9 is a cross-section of a prepared web which may be used forforming the tube;

FIG. 10 shows how the web is folded to form a peripherally grooved rodof uniform cross-section;

FIG. 11 shows a modified rod cross-section; and

FIG. 12 shows diagrammatically a complete apparatus for making filtersfrom the web shown in FIG. 9.

The filter element shown in FIG. 1 consists of a rod section 2 havingsix axially extending peripheral grooves 4 separated by ribs 6 which areof uniform thickness and extend radially, as shown in FIG. 2. Endportions 6A of the ribs are pinched together to close alternate grooves4 at opposite ends. Accordingly, when the filter element is surrounded,for example, by a cylindrical paper wrapper (not shown), alternategrooves form axial passageways through which smoke can enter the filterfrom one end; this smoke then passes transversely through the ribs intothe other axial passageways formed by the other grooves, and from therepasses axially out of the other end of the filter.

FIGS. 5 and 6 show how the filter element is formed. A continuous tube 8of filter material is first folded inwards at circumferentially spacedpositions by means of six wheels 10 while the tube is moving axially,the axes of rotation of the wheel 10 being in a common plane normal tothe axis of the tube. The continuous rod thus formed is of uniformcross-section like the sec tion shown in FIG. 2. During further movementof the rod, two sets of pinching wheels engage in the grooves and splaythe ribs apart so as to close the grooves at appropriate positions.

FIG. 6 shows a set of three pinching wheels 12 which engage in alternategrooves. A further set of similar wheels engage in the other grooves ina position downstream of the first set, this set being inclined at tothe first set (that is to say about the axis of the rod). The pinchingwheels may be heated so as to apply heat to the pinched-together ribportions to cause or assist these rib portions to stick together.

FIGS. 7 and 8 show further views of one of the pinching wheels and inparticular show that the pinching wheel has a number ofcircumferentially spaced V- 4 sectioned lobes 12A which engage in thegrooves to splay the ribs apart.

The continuous rod thus formed consists of a succession of filterelements. The rod is finally cut into individual filter elements atregular intervals through the pinched rib portions 6A. However, beforethe rod is cut, it is preferably enclosed in a paper wrapper so that thefinal rod can be joined to a cigarette by means of an encircling band orcork to form a filter-tipped cigarette. As an alternative, eachcross-flow filter element may be placed end-to-end with a short lengthof conventional filter material of circular cross-section, and these twopieces may be joined together by a paper wrapper; the composite filterthus formed may then be joined to a cigarette, with the cross-flowfilter element lying between the conventional filter element and thecigarette, so that the mouth end of the finished cigarette is formed bythe conventional filter.

The tube 8 from which the filter element is formed may for example be ofcellulose acetate or other fibrous filter material with a bonding agentto bond together the fibers and set the filter in the final shape,possibly with the aid of heat. Alternatively it may for example beformed from one or more layers of filter paper, for example such asMyria, which may be fed as a web and formed into a tube with alongitudinal seam, before being folded inwards to form the rod sectionshown in FIG. 2. A further possibility is that the web which is formedinto the tube may include one or more layers of granular, powdery orother particulate material (for example collagen or a collagen-filledsheet material) sandwiched between layers of paper or other sheetmaterial. Alternatively the web may, for example, be a collagen-filledsheet material, for example consisting of a substantially homogenousmixture of cellulose fibers and collagen.

A further way of forming the tube is shown in FIGS. 9 and 10. The tubein this case is formed from a prepared web of uniform cross-sectionshown in FIG. 9. The web cross-section includes six relatively wide V-sectioned grooves 14 and five narrower grooves 15 which extendlongitudinally along the web. After the web has been formed into a tubeby bringing together its edges, the tube is folded inwards at thegrooves 14 by means of six wheels 16 shown in FIG. 10. This foldingoperation is the same as in FIG. 5, except that the web is shaped topromote the folding. The outer edges of the ribs of the rod thus formedlie at points C1 to C6 on the web. At the points C2 to C6, as a resultof the narrow grooves 15, the web has thin hinge portions to promote thenecessary folding.

The filter material formed into the web shown in FIG. 9 is preferably ofuniform density so that the resistance to the flow of smoke transverselythrough the ribs is substantially uniform at all distances from the axisof the filter element. In order to increase the utilization of thefilter material lying within the core contained within the dottedoutline 18 shown in FIGS. and 11, the web may be formed slightlydifferently so that the grooved rod cross-section is as shown in FIG.11. This enables smoke to flow more easily, below the line 20 in FIG.11, in the direction of the arrow. In other words, the grooves in thefilter element are slightly deepened. In this case, as the thicknessof-the rib is not uniform but decreases towards the center of the rod(i.e. below the line 20), the web material may be made more dense in theregion of the grooves 14, to compensate for the reduction in ribthickness.

FIG. 12 shows how a complete succession of filter elements may be made.A fairly wide and loose web 22 of filter material (e.g. fibrouscellulose acetate) is drawn from a bale 24 and is passed round a pulley26, through a device 28 in which the tow is sprayed with a bondingagent, and round a pulley 30 which deflects it towards a drum 32. Thisdrum is formed with a series of axially spaced circumferential ribs soas to have a peripheral cross-section corresponding to the upper surfaceof the web as shown in FIG. 9. The tow is pressed against the drum 32 bya band 34 which is driven at a speed corresponding to the peripheralspeed of the drum 32. As a result the finished web 22A emergeshorizontally at the bottom of the drum 32, the crosssection of the webbeing as shown in FIG. 9. During the passage of the web 22 from the bale24 to the drum 32, the width of the web is reduced towards that of thefinal web shown in FIG. 9. As the web 22 enters the forming channelbetween the drum 32 and the band 34, it is thicker than the finalsection, and it is compressed evenly to its final section.

While the web 22 is being fed towards the drum 32 and is being reducedin width, a number of converging ribs extending along the web may beprovided to enter the thickness of the web in positions corresponding tothe grooves 14 and 15, so that the grooves in the final web are notformed merely by compressing the finished web section by means ofcircumferential ribs on the drum 32. In other words, the thickness ofthe web just before it enters the shaping passage between the drum 32and the band 34 may vary appropriately so that the density of the finalweb in the region of the grooves is substantially the same as thedensity elsewhere.

When the finished web 22A emerges from the bottom of the drum 32, it isformed into a tube by bringing together the edges at C1, and is thenfolded by means of the wheels 16, which are shown diagrammatically inFIG. 12. The peripherally grooved rod 36 which then emerges from theshaping passage between the wheels 16 passes between two sets of wheels38 and 40, each set consisting of three wheels like the wheels 12 shownin FIGS. 6 to 8. One set of wheels engages in alternate grooves, and theother set is inclined at 60 to the first set (i.e. about the axis of therod) so as to engage in the other grooves. The grooves are thus closedat the appropriate regular intervals, as previously described. A paperweb 42 is fed via an adhesive unit 44 and round a pulley 46 to aposition below the filter rod, and is then wrapped and sealed round therod 36. The continuous wrapped rod thus formed is cut into a successionof rod sections by a cut-off device 43. The unit 44 may apply adhesivenot only to the edges of the paper web 42 but also along regularlyspaced longitudinal bands so as to seal the paper to the outer edges ofthe ribs 16.

Adhesive may also be applied to the web 22A to glue together the partsof the tube at the center of the tube in order to prevent smoke passingstraight through the center of the filter.

Upstream of the set of wheels 16 there may be a die arrangementconsisting of parts inside and outside the tube for progressivelyfolding the tube towards its final peripherally grooved shape. The innerdie member would in this case project into the tube from a position tothe right of the wheels 16 and would taper to a point, so as to end justupstream of the wheels 16. The outer die member would have a circularinternal crosssection at its upstream end, just larger than the tube 8,and its internal cross-section would progressively change towards theexternal cross-section of the tinished rod as shown in FIG. 10. In thiscase, the wheels 16 may simply apply the finishing touch to the foldingoperation, or they may be omitted; if the wheels 16 are omitted then thewheels 12 may, between the lobes 12A, have a cross-section similar tothe wheels 16.

Between the wheels 16 and the wheels 38, the rod may be confined to itsfolded shape by being passed through a close-fitting tube of circularcross-section. Adhesive may be applied to the abutting inner faces ofthe two sections of the web which form each rib, but as an alternativethe tube between the wheels 16 and 38, and the tube formed further on bythe paper wrapper, may be relied upon to hold the web to its finalcrosssection simply by preventing expansion of the folded form.

In order to bond together the fibers ofthe material forming the web, thedrum 32 may be heated. In addition, or as an alternative, the web may bepassed through a heating chamber just before entering the forming spacebetween the drum 32 and the band 34; in this heating chamber, hot air orsteam may be circulated to melt the bonding agent (in the case of athermoplastic adhesive) or to drive off the bonding agent if the bondingagent is a plasticizer.

Instead of the two sets of wheels 38 and 40 being used to closealternate grooves, there may be one set consisting of six narrowcircumferentially spaced wheels each rotatingabout an axis inclined tothe axis of the rod so that successive wheels overlap one another.

As already mentioned, instead of a shaped web (i.e. as shown in FIG. 9)being formed into the tube which is subsequently folded to form the rod,the web may be of uniform thickness and may be formed from one or morelayers of filter paper. In this case the folding of the tube may be doneentirely by means of inner and outer die members as already described. Aset of wheels like the wheels 16 may then be used simply or mainly toapply adhesive to the flanks of the ribs at regular intervalscorresponding to the positions at which the pinching wheels 38 and 40are arranged to close alternate grooves. Thus if the adhesive applied bythe wheels 16 is a hot-melt adhesive, this adhesive would begin to setby the time the rod reaches the pinching wheels 38 and 40 and may forman adequate bond after appropriate parts of adjacent ribs are broughttogether by the pinching wheels 38 and 40.

Instead of the rod section having six peripheral grooves, it may forexample have eight or 10 grooves or any other even number of grooves.

instead of each finished filter element being as shown in FIG. ll, itcould be twice as long. For example, the

continuous rod could be cut through alternate sets of pinched-togetherrib portions; alternatively the finished filter elements could be of thesame length (i.e., twice the distance between successive sets ofpinchedtogether rib portions) with the ends being mid-way between thesets of pinched-together rib portions. In the first example the smokefrom the cigarettes passes twice through the ribs.

We claim:

1. Apparatus for making cross-flow filter elements for cigarettes andother similar articles, comprising means for forming a continuous rod offilter material including a number of substantially axial groovesseparated by rib portions; means for closing alternate grooves atregular intervals by pinching together the ribs; and means for cuttingthe rod at regular intervals to form a succession of cross-flow filterelements.

2. Apparatus according to claim 1 in which the continuous grooved rod isformed by folding inwards circumferentially spaced regions of acontinuous tube.

3. Apparatus according to claim 2 in which the continuous tube is formedby bringing together the edges of a continuous web of filter material.

4. Apparatus according to claim 3, including means for forming in theweb longitudinal grooves along which the web is folded to form thegrooved rod.

5. Apparatus according to claim 4 in which the grooves are formed bypressing the web material against a drum formed with circumferentialribs.

6. Apparatus according to claim 2, in which the tube is folded inwardswith the aid of a number of wheels which have a peripheral cross-sectioncorresponding to the cross-section of the grooves in the rod, and whichrotate with a peripheral speed substantially equal to the speed of therod.

7. Apparatus according to claim 1 in which alternate grooves are pinchedtogether by co-operating wheels which rotate with a peripheral speedequal to the speed of the rod and have lobes which enter the grooves atregular intervals to deform outwards the adjacent portions of the ribs.

1. Apparatus for making cross-flow filter elements for cigarettes andother similar articles, comprising means for forming a continuous rod offilter material including a number of substantially axial groovesseparated by rib portions; means for closing alternate grooves atregular intervals by pinching together the ribs; and means for cuttingthe rod at regular intervals to form a succession of cross-flow filterelements.
 2. Apparatus according to claim 1 in which the continuousgrooved rod is formed by folding inwards circumferentially spacedregions of a continuous tube.
 3. Apparatus according to claim 2 in whichthe continuous tube is formed by bringing together the edges of acontinuous web of filter material.
 4. Apparatus according to claim 3,including means for forming in the web longitudinal grooves along whichthe web is folded to form the grooved rod.
 5. Apparatus according toclaim 4 in which the grooves are formed by pressing the web materialagainst a drum formed with circumferential ribs.
 6. Apparatus accordingto claim 2, in which the tube is folded inwards with the aid of a numberof wheels which have a peripheral cross-section corresponding to thecross-section of the grooves in the rod, and which rotate with aperipheral speed substantially equal to the speed of the rod. 7.Apparatus according to claim 1 in which alternate grooves are pinchedtogether by co-operating wheels which rotate with a peripheral speedequal to the speed of the rod and have lobes which enter the grooves atregular intervals to deform outwards the adjacent portions of the ribs.